Can you help me with the following questions?
1) My book says that instruction is not the same as operation, even though the two are very similar. What is the difference between the two?
2) In the old CPUs when one would store a value into the accumulator register, this value would be automatically added to the value previously stored in accumulator. Thus if accumulator has value 16 stored in it, and if we then try to store value 20 in accumulator, then the two values 16 and 20 will be added and their sum 36 will be stored in accumulator. Is that still true with modern CPUs? If not, then what is todays function of accumulator register? Just to store data?
3) We can access more than one successive byte in main memory. Is something similar also possible with registers? Meaning if register is 32 bit, can we also access just one of the bytes in this register or will CPE read all 4 bytes even if we are only interested in 1 byte?
thanx in advance